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-rw-r--r--syntax-highlight/parsers.scm10
1 files changed, 10 insertions, 0 deletions
diff --git a/syntax-highlight/parsers.scm b/syntax-highlight/parsers.scm
index 5349296..bb967db 100644
--- a/syntax-highlight/parsers.scm
+++ b/syntax-highlight/parsers.scm
@@ -33,6 +33,7 @@
parse-lift
parse-never
parse-map
+ parse-filter
parse-either
parse-both
parse-any
@@ -77,6 +78,15 @@
"Return a new parser that applies PROC to result of PARSER."
(parse-bind (parse-lift proc) parser))
+(define (parse-filter predicate parser)
+ "Create a new parser that succeeds when PARSER is successful and
+PREDICATE is satisfied with the result."
+ (lambda (stream)
+ (let-values (((result remaining) (parser stream)))
+ (if (and result (predicate result))
+ (values result remaining)
+ (parse-fail stream)))))
+
(define (parse-either first second)
"Create a parser that tries to parse with FIRST or, if that fails,
parses SECOND."